It essentially allows you to ignore a specific user, so that their posts will be masked from your view. This is especially handy if you're trying to ignore someone who is flame-baiting or just generally being a nuisance.
To ignore them, click on their nick to take you to their member listing. On the top right there is a drop-down menu that says 'Profile Options'. On this menu is the option to add this user to your ignore list, which can also be managed from your profile page.
I've just enabled this for one of our OTW subscribers, and my blood pressure is much better now. Try it, it's fun
